Methods for laser ablation analysis

ABSTRACT

Methods for laser induced ablation spectroscopy are disclosed. A sample site position sensor, and stage position motors can move the stage in three independent spatial coordinate directions, and a stage position control circuit is used to move an analysis sample site to selected coordinate positions for laser ablation. Light emitted from a plasma plume produced with laser ablation can be gathered into a lightguide fiber bundle that is subdivided into branches. One branch can convey a first portion of the light to a broadband spectrometer operable to analyze a relatively wide spectral segment, and a different branch can convey a second portion of the light to a high dispersion spectrometer operable to measure minor concentrations and/or trace elements. Emissions from a plasma plume can be simultaneously analyzed in various ways using a plurality of spectrometers having distinct and/or complementary capabilities.

CROSS-REFERENCES TO RELATED APPLICATIONS

This present application is a continuation of co-pending applicationSer. No. 13/492,923 filed Jun. 10, 2012, which is a continuation in partSer. No. 12/435,970 filed May 5, 2009 which claims the benefit of U.S.Provisional Application No. 61/126,633 filed May 5, 2008 all of whichare hereby incorporated by reference for all purposes.

FIELD OF THE INVENTION

The present disclosure relates generally to the art of chemicalanalysis, and more particularly relates to improved apparatus andmethods for monitoring the composition of a substrate usingspectroscopies based on laser induced ablation.

BACKGROUND

Restriction of hazardous substances by statutes such as the Directive onthe Restriction of the Use of Certain Hazardous Substances in Electricaland Electronic Equipment 2002/95/EC (commonly referred to as theRestriction of Hazardous Substances Directive or RoHS) was adopted inFebruary 2003 by the European Union. The state of California has passeda similar law. The directive restricts the use of six hazardousmaterials in the manufacture of various types of electronic andelectrical equipment. The six hazardous materials include Lead, Mercury,Cadmium, Hexavalent chromium (Cr-VI or Cr6+), Polybrominated biphenyls(PBB), and Polybrominated diphenyl ether (PBDE).

Industry seeks efficient and economical measures to comply with RoHS.Dissolution in acid is commonly used to test and measure compositionalqualities of sample material. This method has inherent disadvantages.Laser induced breakdown optical emission spectroscopy (LIBS) as well asother laser spectrometry methods are potentially efficient andeconomical techniques to determining and/or verify the composition ofproducts and other materials.

The LIBS type of spectrometry has been an unreliable and inexactmeasurement system since there is a large variation in the recordeddata. A factor is the inconsistent plasma plume created by the pulselaser. Former LIBS type analyses have been unsuccessful in matchingknown standards achieved with other analysis methods.

SUMMARY

In a first aspect of the present disclosure, a laser ablationspectroscopy apparatus is provided. A pulsed laser is focused on asample site to generate a plasma plume during a laser ablation process.The plasma plume can be detected with an optical spectrometer having anintensified charge coupled device. A sample of material is coupled to astage movable in independent x, y and z directions using an array ofx-y-z motors. A change in the height of the sample is detected using asensor. Preferably, the sensor is a triangulation sensor. The apparatusincludes a system computer for synchronizing the movement of the stagein the x, y and z direction during the laser ablation process. Theheight of the sample site can be automatically adjusted following eachlaser ablation. In one embodiment, the system computer includes acontroller, application software and a graphical user interface (GUI).

In another aspect of the present disclosure, a method of laser ablationspectroscopy is provided. The method includes a protocol of generatingone or more laser ablations to a sample site. The spectral data of thetotal number of laser ablations for the sites are averaged together. Insome embodiments, the total number of laser ablations for a sample siteequals three laser ablations. The protocol includes laser ablatingadditional sample sites and averaging the spectral data of the totalnumber of sample sites. In some embodiments, there can be more than 20sample sites.

Other features will become apparent from consideration of the followingdescription taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS

Various embodiments are illustrated in an exemplary manner by theaccompanying drawings. The drawings and accompanying description shouldbe understood to explain principles of the embodiments rather than belimiting. Other embodiments will become apparent from the descriptionand the drawings:

FIG. 1 a simplified diagram of a laser ablation apparatus embodiment.

FIG. 1A is another diagram of a laser ablation apparatus embodiment.

FIG. 2 illustrates a detail of a laser ablation graphical userinterface.

FIG. 3 illustrates a plan view of a testing protocol.

FIGS. 4A and 4B illustrate side views of a topology of a sampleaccording to an embodiment.

FIG. 5 illustrates a plot of spectral information according to anembodiment.

FIG. 6 illustrates a plot of intensities of known standards according toan embodiment.

FIG. 7 illustrates a process flow diagram for a method of ablating.

FIG. 8 is a simplified diagram of apparatus for laser induced ablationspectral analysis including LIBS and LA-ICP-MS.

FIG. 9 is a simplified diagram of apparatus for laser induced ablationspectroscopic analysis comprising collection optics modules and fiberbundles to couple optical emission to spectrometers.

FIG. 10 is a simplified diagram showing an apparatus for LIBS havingoptical collection modules and lightguides for an internal and optionalspectrometer modules.

FIG. 11 is a simplified diagram of apparatus for laser induced ablationspectroscopic analysis for LIBS having one optical collection modulecoupled to an optical fiber bundle having split ends for an internalspectrometer and an optional spectrometer module.

FIG. 12A is an isometric view of an optical frame for an LIBS apparatus.

FIG. 12B is an overhead view of the optical frame shown in FIG. 12A.

FIG. 13 is a side view of the optical frame shown in FIGS. 12A and 12B.

DETAILED DESCRIPTION

Systems, methods, compositions, and apparatus for providing novel laserinduced ablation spectroscopy are disclosed. In various embodiments, anapparatus comprises a sample site position sensor, stage position motorsoperable to move the stage in three independent spatial coordinatedirections, and a stage position control circuit to move an analysissample site to selected coordinate positions for laser ablation, with nohuman interaction. The ablation of material from an analysis sample sitecan displace its position from a point where the laser beam has apredetermined spot size. The embodiments can have a laser positionsensor to detect a change in the position of the sample site andgenerate a displacement signal operable for the stage position controlcircuit to return the sample site to an original position using thestage motors.

In various embodiments, collection optics can gather light from a plasmaplume produced with a laser ablation. The collection optics can couplethe gathered light into a first end of a lightguide through which thelight can be transmitted to a spectrometer. The lightguide can be asingle fiber optic bundle including a plurality of optical fibers heldgenerally parallel to one another in a geometric arrangement. However insome embodiments, the various fibers in the single bundle (trunk) at thefirst end can advantageously be subdivided into smaller bundles (e.g. aplurality of branches) to divert various portions of the light to two ormore spectrometers. Depending on the application, different branches canconvey distinct preselected fractions of the light from the trunk todifferent spectrometers. For example, in an embodiment one branch fromthe trunk fiber bundle can convey a first portion of the light to abroadband spectrometer operable to analyze a relatively wide spectralsegment, and a different branch can convey a second portion of the lightto a high dispersion spectrometer operable to measure minorconcentrations and/or trace elements. Emissions from a plasma plume canthereby be simultaneously analyzed in various ways using spectrometershaving distinct and/or complementary capabilities. For example, aspectrometer having a high speed gated detector, a spectrometer having ahigh speed intensified detector (i.e. an ICCD), a spectrometer having anelectron multiplying charge coupled device (EMCCD), and/or aspectrometer having enhanced sensitivity and/or selectivity inparticular wavelength regions and or at particular wavelengths, can allreceive and analyze radiation from the same plasma plume carried throughdifferent branches. It will be understood that various advantageousspectrometer characteristics may not be exclusive. For example, aspectrometer can be configured with a type of detector particularly wellsuited to the characteristic light throughput (efficiency) andresolution of its dispersive element(s), as well as being selectivelygateable to detect light exclusively in a preselected interval followingeach laser pulse. In particular, an intensified multichannel chargecoupled device detector can be intensified to provide very highsensitivity relative sensitivity, and/or can be synchronously gated onduring a short interval following each laser pulse to discriminateagainst background continuum radiation.

The terminology herein is for the purpose of describing particularembodiments and is not intended to be limiting of the invention. It willbe understood that, although the terms first, second, etc. may be usedto describe various elements, these terms are only used to distinguishone element from another, and the elements should not be limited bythese terms. For example, a first element could be termed a secondelement, and similarly a second element could be termed a first element,without departing from the scope of the instant description. As usedherein, the singular forms “a”, “an” and “the” are intended to includethe plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises,”“comprising,” “includes,” “including,” and/or “having,” as used herein,are open-ended terms of art that signify the presence of statedfeatures, integers, steps, operations, elements, and/or components, butdo not preclude the presence or addition of one or more other features,integers, steps, operations, elements, components, and/or groupsthereof. Reference in the specification to “one embodiment”, “anembodiment”, or some embodiment, etc. means that a particular feature,structure, or characteristic described in connection with the embodimentis included in at least one embodiment. The appearances of the phrase“in one embodiment” in various places in the specification are notnecessarily all referring to the same embodiment, nor are separate oralternative embodiments mutually exclusive of other embodiments.

As used here, various terms denoting spatial position such as above,below, upper, lower, leftmost, rightmost and the like are to beunderstood in a relative sense. The various aspects of the apparatusesdescribed herein are operable without regard to the spatial orientationof the apparatuses as a whole. For example, an apparatus can beconfigured in a vertical orientation or in a horizontal orientation.Hence a component or module that is described as being above anothercomponent or module in a first embodiment having a first orientation,could equivalently be described as being to the left of the othercomponent or module in an equivalent second embodiment configured to bein a second orientation 90 degrees counterclockwise with respect to thefirst.

The term module refers to a distinct unit that is operable to perform anidentifiable function. A module can be a self-contained physical unit orpiece of equipment. A module can also be a logical component effectuatedby a processor and tangible media having instructions and/or data thatare operable for the processor to perform the identifiable function. Theterm automatic refers to a module, service, or control system that isoperable to perform with no human interaction. Monitoring or sensingrefers to measuring a physical quantity. Monitoring is often performedfor the purpose of regulation or control.

The term gas or gas phase species as used herein includes species notbound to each other that have thermal and/or directed motion in a gasphase. The term is not limited by a specific value of a mean free pathbetween collisions. Hence the term “gas phase species” includes variousdifferent species in vapors, atomic or molecular beams, and gaseoussuspensions such as aerosols, and the like.

A lightguide refers to a transmission channel for the directedtransmission of luminous electromagnetic radiation over a distance. Alightguide can include one or more fine filamentary optical fiberscomprised of dielectric material such as silicon dioxide, a transparentpolymer, and the like. The outer surface of each individual opticalfiber can have a cladding of relatively lower refractive index. Alightguide have a cross section that is circular, rectangular, U-shaped,ribbon-shaped, and others. The cross section can be solid or it can behollow. By way of further example, a lightguide can be covered with ajacket comprised of transparent material, opaque material, and others.

The term spectrometer is generally used to identify an instrument thatcan used to view and/or analyze a characteristic of a substance. Withreference to LIBS, an optical spectrometer (also referenced as“spectrometer”) is an instrument operable to separate and detectdifferent wavelength components in electromagnetic radiation within arange of about 180 nm to 1000 nm (ultraviolet to infrared). However,depending on the context, the term optical spectrometer (“spectrometer”)can also be understood to mean the subsystem in an optical spectrometeroperable to disperse and/or separate various wavelength components ofthe electromagnetic radiation (e.g. a monochromator or polychromatorexclusive of an electromagnetic radiation detector). The intendedmeaning can be understood from the context.

The term a mass spectrometer (MS), as used herein, references aninstrument that can separate and detect ions gas based on their chargeto mass ratio. The term inductively coupled plasma mass spectrometer(ICP-MS) will be understood to mean an analysis instrument based onionizing gaseous species in a high temperature inductively coupled(thermal) plasma, extracting such ionized species from the plasma, anddetermining their composition with a mass spectrometer.

The present teachings may be embodied in various different forms. In thefollowing description, for purposes of explanation, numerous specificdetails are set forth in the description and drawings in order toprovide a thorough understanding of the various principles. Furthermore,in various instances, structures and devices are described and/or drawnin simplified and/or block diagram form in order to avoid obscuring theconcepts. However, it will be apparent to one skilled in the art thatthe principles can be practiced in various different forms without thesespecific details. Hence aspects of the invention should not be construedas being limited to the embodiments set forth herein.

FIG. 1 shows a schematic overview of a laser ablation apparatus 100according to the present invention. The apparatus 100 generally includesa pulse laser 102, a stage 106, a position sensor 112, a spectrometer120 and a system computer 140. The apparatus 100 is configured togenerate laser pulses from the pulse laser 102. The laser pulses arefocused onto a sample 105 with a lens 104 to produce a plasma plume 114of the sample 105 at a sample site 110. The position sensor 112 iselectrically coupled with the system computer 140 for sending adisplacement error signal to automatically correct positioning of thestage 106 during an ablating process as describe further below. Theapparatus 100 can include a system frame for housing the variouscomponents described herein. The system frame can include an air filterfor filtering contaminants produced during the ablating process.

The pulse laser 102 in an exemplary embodiment comprises a neodymiumdoped yttrium aluminum garnet (Nd:YAG) laser for generating energy inthe near infrared region of the electromagnetic spectrum with awavelength of 1064 nm. The pulse duration can be approximately 4 ns forgenerating a laser beam with a power density that can exceed oneGW/cm.sup.2 at a focal point or ablation impact point. The laser 102 canhave a repetition rate of approximately 10 hz or alternately lower than10 hz in some embodiments. Alternatively, the pulse duration can vary totens or hundreds of nanoseconds. In another embodiment, the pulseduration can be shortened to ultra short femtoseconds. The lens 104comprises an objective lens used to focus the laser beam on a surface ofthe sample site 110. The laser beam can be focused to a spot size ofapproximately 10-500 micrometers on the sample site 110. In an exemplaryembodiment, the laser beam can be focused to a spot size ofapproximately 150-200 micrometers on the sample site 110.

In an alternative embodiment, a spark generator can be used as theablation source instead of the pulse laser 102. An electric spark ispassed through a sample material until the sample material reaches atemperature where characteristic spectral emissions can be detected. Inan exemplary embodiment, the electric spark can be controlled in anargon atmosphere. A person of ordinary skill in the art can appreciatethe construction of such spark generators in spark spectroscopy systems.

A dichroic mirror 107 is used for directing the laser beam toward thesample site 110 and a mirror 109 allows viewing of the sample site 110using a video camera 116.

The stage 106 includes an attached array of ‘x-y-z’ motors 108 forproviding translation of the stage 106 in a three dimensional space. Thex-y-z motors can comprise suitable stepper motors driven by steppingmotor controllers (not shown), as known by a person of skill in the art.In one embodiment, the stage 106 can have a translation rate ofapproximately 10 cm/s. The stage 106 can include a sample securingmeans.

The position sensor 112 preferably comprises a laser triangulationsensor. The position sensor 112 preferably uses the principle oftriangulation to determine changes in height of the stage 106 and theassociated sample 105. As shown in greater detail in FIG. 1A,triangulation occurs when the position sensor 112 emits a triangulationlaser beam 113 that is focused on the sample site and a first reflection115 a is sensed by a photodetector within the position sensor 112. Achange in height of the sample site 110 causes a displacement in thetriangulation laser beam 113 to produce a second reflection 115 b and adisplacement signal generated by the position sensor 112 is communicatedto a system computer 140. The system computer 140 provides positioninginformation to maintain an optimum height of the sample site. Theposition sensor 112 can comprise a suitable laser displacement measuringdevice as known to a person of skill in the art. In one embodiment, thetriangulation laser 113 coincides with a spot circle of the laser 102generated at the sample site. The triangulation laser 113 can also beused as a targeting marker when selecting a specific point on the samplesite 110 as seen with the video camera 116 as the triangulation laser113 can produce a visible spot on the surface of the sample site 110.

The spectrometer 120 (FIG. 1) collects electromagnetic information fromthe plasma plume 114. The spectrometer 120 can be a monochromator or apolychomator with a detector. The electromagnetic information includesspectral information identifying an elemental composition of the samplesite 110. A spectral range for the spectrometer 120 can be chosen tosuit different applications. In an exemplary embodiment the spectralrange can be approximately 35 nm for observing a portion of theelectromagnetic wavelength range. Alternatively, the spectrometer 120can detect electromagnetic radiation in a range of 200 to 900 nm.Collection optics 122 receive light and plasma lumina generated from theplasma plume 114 and transmits the light and plasma lumina through afiber cable 124 to the spectrometer 120. The collection optics 122 canbe orientated horizontally as shown in FIG. 1. Alternatively, thecollection optics 122 can be orientated at any angle above the sample105 surface plane. A mirror (not shown) within the spectrometer 120reflects the plasma lumina to a grating that disperses the plasmalumina.

An intensified charge coupled device (ICCD) or detector 130 is coupledwith the spectrometer 120 for detecting the dispersed plasma lumina. Thedetector 130 provides the detected plasma lumina to the system computer142. The system computer 140 generates spectral information from theplasma lumina of the laser plume 114. The spectral information includesintensity data representing elemental information and composition of thesample site 110. The spectral information can be produced on a display142.

The detector 130 provides increased resolution and greater selectivityof the spectral information. The detector 130 includes a microchannelimage intensifier plate. The intensifier plate is preferably gatedduring period of time when the plasma plume 114 emits characteristicatomic emission lines of the elements. This period coincides with anoptimum plume luminance period. This period follows emission ofcontinuum radiation. Continuum radiation lacks useful specific speciesor elemental information. In one embodiment, a delay generator (notshown) can be included to provided gating of the detector 130 to allowtemporal resolution of the detector 130 response time. Alternativeembodiments of the detector 130 can include a detector other than anICCD, for example a suitable charge coupled device (CCD) or suitablephotomultiplier. Accuracy of the spectrometer 120 and detector 130 inone embodiment can generate compositional data in the range of 20 ppm orless. Alternatively, the accuracy can be in the range of a few %. Inanother embodiment, the accuracy can be in the range of 1%, which isapproximately 10,000 ppm.

The system computer 140 can include application software and acontroller in the system computer 140 for providing synchronization ofthe laser 102, spectrometer 120, detector 130, position sensor 112 andthe x-y-z motors 108 positioning of the stage 106. The system computer140 is electrically coupled with the laser 102, spectrometer 120,detector 130, position sensor 112, the x-y-z motors 108 and the camera116. The system computer 140 includes a display 142 for displayingspectral information. The system computer 140 can present the spectraldata generated on the display 142. Alternatively, a separate personalcomputer can also be coupled with the system computer 140 for separatelyanalyzing the spectral information. The system computer 140 can includea power controller to regulate power to all the apparatus 100components.

The application software decodes the spectral information from thedetector 130 and facilitates analysis of the spectral information andgenerates composition information of the sample 105. In one embodiment,the intensity data of an elemental peak is subtracted from backgrounddata of the elemental peak to calculate a change in intensity (delta I).The application software allows setting of certain parameters forperforming the laser ablations of the sample site 110. A laser spotcircle size can be set as a parameter and can be consistently andprecisely maintained through the laser ablation process described infurther detail below. Alternatively, a z value for the sample site 110can be set as a parameter and can be consistently and preciselymaintained through the laser ablation process. The spot circle increasesor decreases depending on the change in height of the sample site 110.Keeping the laser 102 spot circle precisely adjusted insures that thesample site 110 produces the plasma plume 114 with consistent optimumplume luminance. Height changes in the sample site can be detected bythe position sensor 112 and a correction to the height of the samplesite 110 is generated by the controller within the system computer 140.The application software and the controller generate correction signalsto reposition the height of the stage 105 after each laser ablation ofthe sample site.

FIG. 2 shows a representative graphical user interface (GUI) 200according to an embodiment of the present invention. The GUI 200includes a first data window 218 and a second data window 220. The firstdata window 218 provides real-time video of a sample site 110. A spotcircle 118 can be observed on the sample site 110 during and followingan ablation. The second data window 220 provides spectral informationgenerated from the system computer 140. In an exemplary embodiment, thespectral information includes a waveform 222 representing intensity andwavelength data of a sample site ablation.

FIG. 3 shows a top view 300 of a protocol for ablating a sample 305according to an embodiment of the present invention. The protocolincludes ablating multiple sample sites 312. In an exemplary embodiment,the sample sites can be uniformly and evenly distributed throughout asurface of the sample 305. Alternatively, the sample sites 312 can berandomly distributed through the surface of the sample site. The numberof sample sites 312 ablated can vary depending on a particular sample ora particular application. In one embodiment, the number of sample sitescomprises twenty. Alternatively, the number of sample sites can be tenor fewer. In another embodiment, the number of sample sites can bethirty or more.

The protocol 300 can include a specific number of pulse laser ablationsper sample site 312. Heterogeneous material can include elements havingvarying thermal properties. A single shot laser ablation can vaporizedisproportionately more volatile elements than the less volatileelements. Spectral information from a single ablation may not be areliable indication of the composition of the sample 305. In anexemplary embodiment, the number of laser ablations per site comprisesthree laser ablations. Alternatively, the number of laser ablations persite comprises two. In another embodiment, the number of laser ablationsper site comprises a single laser ablation. In still another embodiment,the number of laser ablations per site comprises four or more laserablations.

FIGS. 4A and 4B show side views of a first sample 405A and a secondsample 405B according to an embodiment of the present invention. Thefirst sample 405A comprises a material having sample sites 410A withsubstantially uniform topology. The height of the sample sites 410A aresubstantially the same. The second sample 405B, however, comprises amaterial having sample sites 410B with erratic or varying topology. Theheight of the sample sites 410B can be different. The apparatus 100 isconfigured to provide consistent spectral data for either the uniformsample sites 410A or sample sites 410B with varying heights. The systemcomputer 140 adjusts the height of the stage 106 to achieve the optimalplasma lumina.

FIG. 5 shows a plot 500 of spectral data according to an embodiment ofthe present invention. The plot 500 includes a waveform plotted along awavelength (nm) versus an intensity (a.u.). An elemental peak ‘A’ canrepresent the spectral information for the element Lead (Pb). Theelemental peak ‘B’ can represent spectral information of a differentelement.

FIG. 6 shows a plot 600 of compositional data 600 according to anembodiment of the present invention. The plot 600 includes a waveformplotted along a composition (nm) versus an intensity (a.u.). The plot600 is generated by performing laser ablation according to the methoddescribed herein on a known standard sample. The known standard producesintensities 11, 12 and 13 for associated elements at the respectivecompositions 34 ppm, 146 ppm and 406 ppm. Quantitative analysis ofdifferent elements of a particular sample is performed by comparingspectral data of the particular sample with the compositional data 600.For example, spectral information obtained from analysis with theapparatus 100 can include intensity 14. The quantity of the element canbe approximated to 90 ppm.

FIG. 7 shows a process flow diagram for a method 700 of laserspectroscopy according to an embodiment of the present invention. Thelaser ablation apparatus 100 (FIG. 1) is used as an example. The method700 begins at the step 710. In one embodiment, the method 700 can befully automated using application software included in the systemcomputer 140. A specific protocol can be entered into the applicationsoftware instructing the application software of desired parameters orsettings for the apparatus 100. Alternatively, the method 700 can bemanually performed. At the step 720, a laser pulse is generated toablate the sample site 110 into an emissive plasma plume. A real-timevideo image of the sample site 110 is generated on a first window 218 ofthe GUI 200. The real-time video is received from the video camera 116.The plasma plume 114 is analyzed by the spectrometer 120 and thedetector 130. The plasma lumina and the electromagnetic radiationgenerated by the plasma plume is optically communicated to thespectrometer 120 and detected by the detector 130. The position sensor112 provides a displacement signal to the system computer 140 indicatingany change in the height of the sample site 110. The system computerreceives spectral information from the spectrometer 120 and the detector130.

At the step 730, the system computer 140 generates spectral andwavelength information for presentation on the display 142. In oneembodiment, intensity and wavelength data are represented as waveformson the GUI 200. The waveform is presented in a second window 220 of theGUI 200 and includes the intensity and wavelength data. In anotherembodiment, a second waveform is superimposed on the first waveform 222in the second window 220. The second waveform can include additionalspectral information. For example, particle imaging information,tracking information or scaled or gated representations of the firstwaveform 222.

At the step 740, the steps 720 and 730 are repeated for each sample siteon the sample. The spectral data for a total number of laser ablationsfor the sample site 110 can be averaged together. In an exemplaryembodiment, the total number of laser ablations for the sample site 110equals three laser ablations. The spectral data of the three laserablations are averaged together to generate a ‘site sum’. The site sumis a reliable and accurate representation of the elemental compositionof the sample 105 at the sample site 110. Alternatively, the site sumcomprises spectral data from two laser ablations. In another embodiment,the site sum comprises spectral data from one laser ablation. In stillanother embodiment, the site sum comprises spectral data from four ormore laser ablations.

At the step 750, the site sum can be compared with spectral informationgenerated from performing the method described herein on a knownstandard material. The known standard material comprises specific knownelements at a known composition. Laser spectroscopy performed on theknown elements generates known spectral data including known intensityvalues. An elemental composition for the sample site 110 can beapproximated by comparing the site sum with the known standard spectraldata.

At the step 760, the steps 720 through 750 can be repeated for one ormore additional sample sites to generate additional site sums. Thespectral data for the total number of site sums can then be averagedtogether. In an exemplary embodiment, the total number of site sumsequals twenty. The spectral data of the twenty site sums can be averagedtogether to generate a ‘sample sum’. The sample sum is a reliable andaccurate representation of the elemental composition of the sample 105as a whole. Alternatively, the total number of sites sums can be ten orfewer. In another embodiment, the number of sites sums can be thirty ormore.

The apparatus 100 can perform laser ablation or laser induced breakdownspectroscopy (LIBS) on a variety of materials. The materials can beheterogeneous or homogeneous solids or semi-solids. Alternatively, thematerials can comprise a liquid or even a gas. In another embodiment,the apparatus 100 can be used for LIBS on biological materials. Analysisof biological material can include building a library of known spectralsignatures including elemental and compositional data for specificbiological material. The spectrometer 120 can collect and detect withthe detector 130 spectral information on a broad range from 200 to 900nm. An unknown biological sample can be compared with the library todetermine the biological substance. The method ends at the step 780.

In an alternative embodiment, the method 700 can be used in a remoteconfiguration. The sample material is positioned in a location that isremote from the ablation source or laser. A telescopic device can beintegrated with the apparatus 100 to provide optical coupling of plasmalumina. The generation and analysis of spectral data can proceedsimilarly as described herein. Furthermore, other spectroscopies, inplace of and/or in addition to optical emission spectroscopies can beused to obtain characteristic ablation spectral data within the scope ofthe present invention. For example, laser ablation inductively coupledplasma mass spectrometry (LA-ICP-MS) can be applied in conjunction withand/or as an alternative to the LIBS technique described herein.

Still further embodiments can be understood with respect to FIGS. 8-13B.Like numerals in FIGS. 8-13B designate corresponding elements.

FIG. 8 is a simplified drawing of a system for laser induced ablationspectral analysis of a sample. The system has a movable stage 8225coupled to x-y-x translation motors (not shown) that can move a sample8310 on the stage in three independent directions. The system also has alaser 8205 that can emit a pulsed laser beam 8210, and has variousoptical elements such as a mirror 8220, laser beam focusing opticsmodule 8416 and/or others that can cooperatively focus the laser beamonto a selected sample site 8217 for ablation. The sample 8310 and stagecan be in an unreactive gaseous atmosphere confined within enclosure8200. The atmosphere in the enclosure can be transparent at wavelengthscomprising pulsed laser beam and/or characteristic spectral emissionemanating from the plasma plume 8010. In a preferred embodiment, thepulsed laser 8205 can be a Nd YAG laser emitting a pulsed laser beamwith a near infrared wavelength of 1064 nm, and the unreactiveatmosphere can be inert gas such as helium and/or argon.

However an ultraviolet wavelength selected from among 193 nm, 266 nm and193 nm is preferred for the ablation for some applications, particularlywhen performing analyses using ICP-MS. UV wavelengths can provide abetter sample of gaseous species from a sample site by comparison to amore conventional pulsed laser wavelength in the near infrared. Short UVwavelengths can be generated as harmonics of longer wavelength exicimerand/or solid state lasers as will be understood by those having ordinaryskill in the art.

Characteristic spectral emission emanating from the plasma plume 8010generated by ablation can be gathered with a collection optics module8410. The collection optics module can couple the spectral emission intoa lightguide 8230. The lightguide can transmit the optical emission toan optical spectrometer comprising wavelength separation unit 8510 anddetector 8550. The collection optics module can include lenses 8412,8414 and/or other optical elements and is disposed in a preselectedposition and orientation by optical frame 8440. Further details of anoptical frame structure 8440 are disclosed in FIGS. 12A, 12B and 13. Asshown in FIG. 12A, the laser beam focusing optics module 8445 is securedto frame 8440 in a position where it can center a precise laser spotcircle 9510 of predetermined size in plane 9460 on a point 9500. Plane9460 is a preselected distance 9450 below optical frame 8440.Accordingly, stage 8225 can movably translate a selected sample site8217 (also see FIGS. 9-10) to the center laser spot circle position toperform precise and consistent laser ablation of material from theselected site.

As can be understood with respect to FIGS. 10-13, the optical frame 8440has support substructures 8415, 9415 operable to secure collectionoptics modules 8410 and/or 9410 in a preselected positions withrespective central axis/axes 8416 and/or 9416 of each collection opticsmodule aimed at a situs 9300 of the plasma plume. This arrangementpositions each laser ablation and its ensuing plasma plume in the samelocation relative to the optics support structure 8440. Accordingly,each optics support substructure 8415, 9415 can hold a respectivecollection optics module 8410, 9410 in a fixed position and orientationthat can optimize light collection from a plasma plume arising from thespot circle position.

In various embodiments, a gas flow system such as shown with respect toFIG. 8 can maintain an atmosphere of unreactive carrier gas insample/stage enclosure 8200. A source of pressurized unreactive gas 8350can be coupled to a flow controller 8355 through a fluid channelcomprised of conventional tubing, pipe and/or fittings. The flowcontroller 8355 can deliver a selected flow rate of the carrier gas toenclosure 8200 through fluid passage 8365. Flow controller 8355 can be apneumatic flow controller, an electronic mass flow controller, a fixedorifice, and others. The flow rate can be controlled using a computer8710 to actuate the flow controller and/or provide a setpoint by way ofa communication channel represented by the dashed line between acomputer 8710 and flow controller 8355.

In some embodiments, gaseous laser ablation products 8215 generated inchamber 8200 can be transported in the carrier gas from enclosure 8200to an inductively coupled plasma-mass spectrometer (ICP-MS) 8100 throughflow channel 8366. In various embodiments, the gaseous laser ablationproducts can include permanent gases, vapors, molecular clusters,suspended particles, aerosols and/or others. The inductively coupledplasma-mass spectrometer (ICP-MS) 8100 is operable to perform a furtherspectral analysis of the ablation products based on the mass of ionizedspecies. In various embodiments, the ICP-MS comprises an inductivelycoupled thermal plasma sustained in an inert carrier gas such as argon.Those having ordinary skill in the art will recognize that thermalplasma sustained in the ICP-MS 8100 have sufficiently high temperature(over 5000K) to ionize the gaseous laser ablation products. Ionizedproducts from the thermal plasma are introduced into a mass analyzerwithin the ICP-MS where they can be separated and identified based oncharacteristic charge to mass ratio. Accordingly, the ICP-MS analysiscan provide additional information useful to augment, improve, and/orconfirm an emission spectroscopy determination of sample sitecomposition based on lumina from the plasma plume.

It has also been found that ICP-MS may not be particularly effective todetermine relative relatively light elements (atomic number less thanabout 10) and elements generally found in organic compounds (carbon,hydrogen, oxygen and nitrogen). In this regard, it has been found thatthe LIBS analysis can complement and quantify the concentrations ofvarious elements that may not be acceptably measured using ICP-MS alone.Furthermore, it is difficult to measure high concentrations of elements(bulk composition analysis) in an ICP-MS while simultaneously performingtrace level chemical analysis with the same instrument. On the otherhand ICP-MS is highly sensitive and can perform trace leveldetection/analysis at levels as low as 1 part per billion, and undersome circumstances even lower levels are operable. It has been foundthat a combination of laser ablation emission spectroscopy and laserablation ICP-MS can determine both high concentration level analysis aswell as trace levels at 1 ppm or even 1 ppb of a single sample site,which could not be performed using either laser ablation emissionspectroscopy or laser ablation ICP-MS alone. Yet another advantagehaving both techniques in combination arises from an ability to detectpulse-to-pulse variations in the amount of ablated material based on asignal level in from wideband emission spectra. The emission signals canbe useful to normalize and/or correct the ICP-MS mass/charge intensitiesthereby improving accuracy.

A system with respect to FIG. 8 can include at least one computer 8710.The computer comprises machine readable media operable to store data andinstructions and a processor that can read the data and perform theinstructions. Furthermore, media has various modules operable toeffectuate various control functions, control loops, displays, humaninterfaces, and others. The dashed lines 8720 shown in FIG. 8 representcommunications channels between the computer and various systemcomponents such as pulsed laser 8205, ICP-MS 8100, an opticalspectrometer wavelength separation unit 8510, a spectrometer detector8550, an electronic flow controller 8355, and a stage positioncontroller for x-y-z stage 8255. The system can also includecommunications channels for a sample site position sensor, and otherphysical and/or software components not shown in FIG. 8. It will berecognized that a communication channel can be implemented in variousdifferent ways. For example, data and/or instructions can be carried byway of physical media as point to point wiring, over a parallel bus,over serial and/or parallel fiber optic connections, with a virtualcircuit in a network protocol layer, and/or others.

It will be understood that various embodiments with respect to FIG. 8can further include a number of additional elements and structuresdisclosed in relation to FIGS. 1-7 above. These elements are beenomitted from the drawing to avoid obscuring other concepts simplify theexplanation. By way of example, a system with respect to FIG. 8 caninclude a video camera, a sample site position sensor and an x-y-z stageposition controller in a stage position control circuit, a triangulationlaser, and others. Furthermore, some embodiments do not include all ofthe elements and subsystems shown. For example, there are embodimentswith an ICP-MS. In these embodiments unreactive carrier gas fromenclosure 8200 can be vented into an exhaust line (not shown).

Other embodiments of a system for material analysis using LIBS can beunderstood with respect to the simplified diagram in FIG. 9. A systemwith respect to FIG. 9 comprises a master system module 9400, and canhave an optional extension spectrometer module 9600. The master systemmodule 9400 can include any of the elements and/or structures disclosedwith respect to FIG. 8, including elements not shown in FIG. 9 (e.g. thecarrier gas components 8350, 8355, and others are omitted for clarity).The optical frame 8440 of master unit 9400 is operable to support asecond collection optics module 9410. The second collection opticsmodule can gather spectral emission from a plasma plume 8010 and couplethe light into a second lightguide 9240. Lightguide segment 9241 candeliver spectral emission to extension spectrometer 9600. In someembodiments lightguide segment 9240 in the master module and segment9241 in the extension spectromter module can be portions of one singlecontinuous fiber. In further embodiments, segments 9240 and 9240 can bephysically different fibers optically joined through an interfaceconnection between the master module and the extension spectrometermodule.

An operable system with respect to FIG. 9 can comprise a master systemmodule without any extension spectrometer 9520 (master only). The masteronly configuration can perform laser ablation optical spectroscopy usingspectrometer 9510. Furthermore, a master only system can be fieldreconfigured to add an extension module. An extension model upgrade canadd the capability to acquire emission spectra from a plume from themaster system module spectrometer 9510 and extension spectrometer 9520simultaneously. Spectral data from similar and/or different types ofdetectors in spectrometers 9510 and 9520 can be communicated to computer8710 through communication channels 8720. A collection optics module9410 to acquire plasma plume light emission for the extensionspectrometer module 9600 can be included in master unit module 9400 whenit is shipped from the factory, or a second collection optics modulemodule 9410 can added to an optical frame 8440 in the field. Variousembodiments with respect to FIG. 9 comprise an optical frame 8440 havingcollection optics module support substructures 8415, 9425, shown withrespect to FIGS. 12A, 12B and 13, to hold respective collection opticsmodules 8410 and 9410 in a preselected positions and orientations asshown.

As shown with in FIG. 13, the supporting substructures 8415 and 9415 canhave mirror symmetry with respect one another to be in predeterminedpositions directing the central axis 8416, 9416 of each collectionoptics modules to a point 9300 equidistant from each module, where thepulsed laser 8205 spot circle can generate a precise plasma plume. Thecentral axes 8416, 9416 intersect an x-y plane parallel to the stage atequal angles 8419, 9419, from which each module can view from a plume at9300 and capture equal portions of the light through equal solid anglecones 9350, 9360 subtended by the collection optics modules.

In various other embodiments, a master system module can include one ormore of the additional spectrometers and structures shown in anextension module with respect to 9-11 (e.g. a single master module LIBSsystem can comprise various spectrometers, lightgudes (optical fibers),and others disclosed with respect to FIGS. 9-11), within one physicalunit (the instrument).

Some further LIBS system embodiments can be understood respect to FIG.10. A lightguide fiber optic bundle 8880 connected to collection opticsmodule 8410 can have a bundle of equal diameter fibers at a principal(proximal) end that is subdivided into smaller bundles leading to thedistal split ends 8237 and 8239. Each of the distal split ends canilluminate a separate spectrometer 9510, 9520.

Furthermore, each of the distal split end bundle portions 8237, 8239 canhave different numbers of fibers. Accordingly, luminous flux receivedfrom a collection optics module by the proximal end can be divided amongthe split distal ends in proportion to the number of fibers constitutingeach split end branch. In various embodiments relative to FIG. 10, totalspectral power entering the proximal principal end of fiber bundle 8880from collection optics module 8410, can be split to deliver a relativelysmaller portion of the total power through a split end bundle 8237comprising a relatively smaller number of fibers, and can deliver arelatively larger portion of the total power through a split end bundle8239 comprising a relative larger number of fibers. The smaller portionof power can be delivered to a high sensitivity and/or low efficiencyspectrometer 9510, and the larger portion of the power can be deliveredto a low sensitivity and/or low efficiency spectrometer 9520. It will beappreciated that splitting total power in this manner can providerelatively more illumination where more power is necessary and/ordesired, and relatively less illumination can be directed to aspectrometer where light intensity from the collection optics modulemight otherwise saturate its detector.

Relative to systems having two independent collection modules and twoindependent lightguides disclosed with respect to FIG. 9, use of a spitend lightguide, and/or split end lightguide optical power distributionsystem distribution (FIG. 10) can save the costs associated of a secondcollection module 9410 and/or second collection module support structureelements on the optical frame 8440.

Still further embodiments are disclosed relative to FIG. 11. A systemwith respect to FIG. 11 can provide a first collection optics module8410 configured to couple a maximum portion of acquired luminous powerto spectrometer 9510 through lightguide 8230. Various embodiments canalso have a collection optics module 9410 coupled to the proximalprincipal end of an n-way split end fiber optic bundle. Each split endbranch can convey spectral emission to a separate spectrometer. Anembodiment with respect to FIG. 11 comprises a fiber lightguide assemblyhaving 4 distal split end bundles 8240, 8250, 8260, 8270 configured tocouple to respectively different spectrometers 9520, 9530, 9540 9550.Various further embodiments can have N different spectrometers coupledto a collection optics module with using an N-way split end fiber opticlightguide. There are also embodiments having a plurality of collectionsoptics, where at least two of the modules are coupled to first andsecond pluralities of different spectrometers (e.g. N and M) using N-wayand M-way split end fiber optic lightguides. In this regard, all of thespectrometers in system embodiments disclosed herein can be operable tosimultaneous receive the spectral emission emanating from each plasmaplume generated in a laser ablation of a sample site.

An LIBS system with the capacity to analyze the spectral emission fromthe plasma plume at an ablation site in real time, using a plurality ofoptical spectrometers to receive spectral emission simultaneously,and/or in tandem, has many advantages that enable superior analyticalcapability relative to prior art systems. Wavelength separating elements(monochromators, polychromators, filters, and others) as well as thedetectors (i.e. CCD, ICCD, EMCCD, silicon photodiodes, photomultipliers,and others) useful in an optical spectrometer have absolute and spectralsensitivity limitations that can make it impractical and/or impossibleto have sufficiently high spectral resolution, sensitivity, spectralbandwidth, and temporal resolution in a single optical spectrometerinstrument that is operable to broadly determine a composition ofunknown samples by LIBS multiwavelength analysis in real time. However,an individual spectrometer can be optimized to enhance sensitivity,resolution, and/or temporal resolution over limited range wavelengths.Accordingly, a plurality of optical spectrometers, individual selectedand/or tuned to have optimal characteristics in a limited wavelengthregion, can provide spectroscopic analyses that are beyond capability ofa single spectrometer system.

Analysis of a sample site by optical emission spectroscopy of theablation plasma plume also can be limited by inherent characteristics ofthe plasma plume itself. For example, continuum emission can obscurecharacteristic spectral lines emanating from the ablated material from asample site. As already disclosed above, continuum interference can bediminished and/or eliminated by using a high speed detector that isgated to exclusively detect line emission during a time interval aftercontinuum intensity has decayed. Nevertheless, there are also inherentlimitations arising from spectral overlap, interference, broadening,and/or low emission intensity at certain characteristic wavelengths,that remain difficult and/or impractical to overcome. Emission spectraanalysis has some limitations can be traversed by applying a differentspectral technology. For example, an ICP-MS can perform elemental and/orisotopic composition analyses at material concentrations well below 500ppb, or even less than 1 ppb, that are inaccessible using emissionspectroscopy alone. In various embodiments with respect to FIG. 8simultaneous analysis of gaseous species from a sample site using ICP-MScan provide complementary ion mass to charge ratio peak intensityanalytical information. In various embodiments, computer 8710 hasanalytical software operable to determine the composition of a samplesite based on the spectroscopic data from plasma plume emission and theICP-MS ion mass/charge ratio intensity data as a whole. It is found thatthe analysis based on LIBS optical emission spectroscopy and ICP-MS ionmass/charge ratio peak intensity data as a whole can detect far moreelements, and can have greater analytical accuracy relative to LIBSemission spectroscopy or ICP-MS alone.

A multi-spectrometer system such as disclosed relative to FIGS. 8-11 canhave use different types of optical spectrometers and detectors at thesame time to advantage. Some embodiments comprise a scanning CzernyTurner spectrograph (CZ) coupled to an ICCD detector. This combinationcan effectuate extremely high sensitivity owing to maximal lightthroughput to the ICCD (high efficiency) from the spectrograph, and ICCDcapability to amplify weak signals in the detector. Accordingly it isadvantageous where the highest possible sensitivity is needed to detectnumerous different elements present in the range of 1 to 10 parts permillion. However this combination has the disadvantage that it can onlycapture a relatively narrow range of preselected wavelengths with apredetermined spectral resolution. Furthermore, the wavelength range andresolution vary inversely. The higher the spectral resolution, thenarrower the range of wavelengths that can be covered at one time.Accordingly, to capture high resolution spectral information from atomicelements having spectral emissions in widely separated wavelengthregions using only one CZ-ICCD, the CZ must be sequentially reconfiguredto access each of the separated wavelength regions, and an additionalablation of the sample site must be performed after each reconfigurationto generate the spectral emissions for capture.

An embodiment may also include an Echelle spectrometer coupled to anICCD detector. This combination has the advantageous capability of beingable to capture a broad range of wavelengths at one time in emissionfrom the plasma plume arising from a single ablation (a typical range is200 nm-900 nm, although in a preferred embodiment the range is 190nm-1040 nm and it can be greater). On the other hand, an Echellespectrometer generally has low light throughput (low efficiency). Forexample an Echelle spectrometer can typically have f/10 aperture lightthroughput whereas a typical CZ spectrometer generally has aboutthroughput in the range of f/3 to f/4. It can be seen that anEchelle-ICCD system is insensitive by comparison to the CZ-ICCD.

Accordingly, some embodiments comprise a plurality of CZ-ICCDspectrometers wherein each spectrometer is configured to receive adifferent preselected wavelength range. The plurality of spectrometersas a whole can capture a broad range of wavelengths at one time yet havevery high sensitivity and resolution. The wavelength ranges can becontiguous and/or can be separated. Furthermore, various wavelengthranges can be non-overlapping or can have overlapping segments. All ofthe spectrometers can receive a portion of spectral emission a plasmaplume simultaneously from one collection optics module through a splitend fiber optic lightguide (described above with respect to FIGS.10-11), and/or at least some of the spectrometers can receive equalportions of luminous energy from a dedicated of collection optic moduleas shown with respect to FIGS. 9, 11, and 12-13.

Some further embodiments comprise an array of Czerny Turner-CCD opticalspectrometers (e.g. each comprising a Czerny Turner monochromator withmultichannel CCD detector). Each spectrometer covers a preselected,non-overlapping, wavelength region. The array of spectrometers isoperable to acquire spectral data synchronously from each ablation. Theembodiments have an advantage of being able to capture broadbandspectral information in a wide range of wavelengths. For example, anoperable range of wavelengths can be 190 nm-1040 nm, although a narrowerrange can be preferable for greater resolution, depending on theapplication. In some embodiments there can be overlapping spectrometerwavelength regions. A partially overlapping wavelength region can beuseful to calibrate the response of the different spectrometers regionswith respect to one another using regions of overlap.

The various detectors and monochromators/spectrographs have advantagesand disadvantages with respect to one another. For example, while a CCDdetector is generally less sensitivity than an ICCD, CCD technology isrelatively inexpensive in comparison to an ICCD having an equivalentnumber of channels. A CCD detector is well suited for broadbandanalysis. Besides having less sensitivity, another limitation of CCDdetector arrays is that they cannot be gated on and off in very shortintervals to discriminate against continuum emission and/or otherinterference.

In the analysis of unknown samples, a broadband CCD spectrometer and/orarray of spectrometers can be first used to survey the principalelements that are present, and identify the elements present inmajority, minor, and/or trace concentration levels. After a sample ischaracterized using a broadband optical spectrometer (such as onecomprising a CZ-ICCD or CZ-CCD combination), higher resolution lowerintensity spectral data obtained from a high resolution, lowersensitivity spectrometer and/or plurality of high resolution/highsensitivity spectrometers in an array can be provide trace elementanalysis. As disclosed above, various embodiments can acquire bothbroadband and low intensity, high resolution spectroscopic data from asingle ablation plume simultaneously.

In the foregoing specification, various aspects are described withreference to specific embodiments, but those skilled in the art willrecognize that further aspects are not limited thereto. Various featuresand aspects described above may be used individually or jointly. Otheraspects of the invention, including alternatives, modifications,permutations and equivalents of the embodiments described herein, willbe apparent to those skilled in the art from consideration of thespecification, study of the drawings, and practice of the variousaspects. Further, various aspects can be utilized in any number ofenvironments and applications beyond those described herein withoutdeparting from the broader spirit and scope of the description. Thewritten description and accompanying drawings are, accordingly, to beregarded as illustrative rather than restrictive.

Although various embodiments have been presented and explained usingsimplified examples, it will be understood that various changes andmodifications are possible with regard to materials, shapes, anddimensions, without departure from the scope of the patent claims. Theembodiments and preferred features described above should be consideredexemplary, with the invention being defined by the appended claims,which therefore include all such alternatives, modifications,permutations and equivalents as fall within the true spirit and scope ofthe present disclosure.

What is claimed is:
 1. A method for analyzing the composition of asample using laser ablation spectroscopy, comprising: placing a sampleon a stage being operable to move in x and y directions of a plane andin a z (height) direction perpendicular to the plane and moving saidstage in said respective x and y and z directions, automaticallymaintaining an optimum height of a first sample site on the samplesurface while ablating material from the first sample site into a firstluminous plasma plume; and automatically maintaining the optimum heightof a second sample site while ablating material from the second samplesite into a second luminous plasma plume, wherein the optimum height isautomatically maintained with a stage position controller operable toautomatically adjust a height of the stage using a displacement signalproportional to a difference of height of the first sample site relativeto a height of the second sample site, and the displacement signal isgenerated by a position sensor operable to sense the difference ofheight, gathering light emanating from each plasma plume into a proximalend of at least one lightguide, and transmitting the gathered light to aplurality of distal ends of the one or more lightguides; simultaneouslycoupling transmitted light from each of the distal ends to arespectively associated spectrometer having wavelength separation meansand a detector; receiving wavelength and intensity values from eachspectrometer in a computer having instructions operable to determine arepresentation of the sample composition based on the receivedwavelength and intensity values; and determining a representation of thesample composition with the computer.
 2. The method of claim 1, whereina pulsable laser is used to perform the ablation and produce theluminous plasma plume.
 3. The method of claim 1 wherein the positionsensor comprises a triangulation laser, and the stage position controlcontroller comprises an array of motors operable to move the stage apredetermined amount.
 4. The method of claim 1, wherein the positionsensor displacement signal depends on a laser triangulation of thesample site.
 5. The method of claim 1 wherein the triangulation laserprovides a visible targeting marker on the first sample site and avisible targeting marker on the second sample site.
 6. The method ofclaim 1, wherein at least one of the detectors is insensitive toelectromagnetic radiation during one time interval, and is switched onto receive the electromagnetic radiation during another different timeinterval.
 7. The method of claim 6, wherein the switching is performedwith an electronically gateable device.
 8. The method of claim 1,wherein an element concentration of 20 parts per million or less in thesample is determined.
 9. The method of claim 1, wherein the positioningof the stage, the ablation of the sample, and the receiving light byeach spectrometer are synchronized by a controller.
 10. A method ofdetermining a sample site composition using laser ablation spectroscopywherein spectral data comprising wavelength and wavelength intensityvalues are simultaneously obtained from a plurality of opticalspectrometers, each optical spectrometer having a respective wavelengthseparating element and a detector, the method comprising: providing alaser pulse from a pulsed laser ablation source; using the laser pulseto ablate material from a sample site into an emissive plasma plume;gathering light emanating from the emissive plasma plume into a fiberoptic lightguide having one proximal end and a plurality of distal ends,coupling a relatively smaller portion of the gathered light from a firstdistal end of the fiber optic lightguide into a first associated opticalspectrometer operable to capture a relatively broadband wavelength rangewith relatively low resolution; and simultaneously coupling a relativelylarger portion of the gathered light from a second distal end of thefiber optic into a second associated optical spectrometer operable tocapture a relatively narrow portion of the relatively broadbandwavelength range with relatively high resolution and relatively highsensitivity; receiving the simultaneous broadband spectral data from thefirst associated optical spectrometer and relatively high resolutionspectral data from the second associated optical spectrometer in acomputer having instructions operable to determine a representation ofthe sample site composition based on the simultaneous data received; anddetermining a representation of the sample composition with thecomputer.
 11. The method of claim 10, further comprising: transporting agaseous portion of ablated material from the plasma plume to aninductively coupled mass spectrometer; receiving ion mass to charge peakintensity values from the inductively coupled mass spectrometer in thecomputer; detecting a pulse to pulse difference in the amount ofmaterial ablated from the sample site based on a signal level obtainedfrom the broadband spectroscopic data; determining a sample sitecomposition based on a combination of the wavelength and wavelengthintensity values from each of the optical spectrometers and normalizedvalues of the ion mass to charge ratio peaks, wherein the normalizationcomprises a correction for the pulse to pulse differences in the amountof ablated material based on the signal level from the broadbandspectral data.
 12. A method of determining a sample site compositionusing laser ablation spectroscopy wherein spectral data comprisingwavelength and wavelength intensity values are simultaneously obtainedfrom a plurality of optical spectrometers, each optical spectrometerhaving a respective wavelength separating element and a detector, themethod comprising: providing a laser pulse from a pulsed laser ablationsource; using the laser pulse to ablate material from a sample site intoan emissive plasma plume; gathering light emanating from the emissiveplasma plume into a fiber optic lightguide having one proximal end and aplurality of distal ends, coupling a first portion of the gathered lightfrom a first distal end of the fiber optic lightguide into a highsensitivity and/or low efficiency first spectrometer; and simultaneouslycoupling a second portion of the gathered light from a second distal endof the fiber optic into a low sensitivity and/or low efficiency secondspectrometer; receiving the simultaneous spectral data from the firstand second optical spectrometers in a computer having instructionsoperable to determine a representation of the sample site compositionbased on the simultaneous data received; capturing broadband spectraldata from each respective plasma plume wherein one or more of theoptical spectrometers selected from the plurality of opticalspectrometers are collectively operable to capture the broadbandspectral data; transporting a gaseous portion of ablated material fromthe plasma plume to an inductively coupled mass spectrometer; receivingion mass to charge peak intensity values from the inductively coupledmass spectrometer in the computer; determining a sample site compositionbased on a combination of the wavelength and wavelength intensity valuesfrom each of the optical spectrometers and normalized values of the ionmass to charge ratio peaks, wherein the normalization comprises acorrection for the pulse to pulse differences in the amount of ablatedmaterial based on the signal level from the broadband spectral data.